U.S. patent number 4,861,688 [Application Number 07/029,343] was granted by the patent office on 1989-08-29 for zinc-alkaline battery.
This patent grant is currently assigned to Matsushita Electric Indus. Co. Ltd., Mitsui Mining & Smelting Co., Ltd.. Invention is credited to Keiichi Kagawa, Akira Miura, Ryoji Okazaki, Kanji Takata, Toyohide Uemura.
United States Patent |
4,861,688 |
Miura , et al. |
August 29, 1989 |
Zinc-alkaline battery
Abstract
This invention uses as the anode active material a zinc alloy
containing Ni, at least one element selected from In, Pb, Ga and Cd
and, optionally further, one element selected from Al, Mg, Ca, Ba
and Sr for the anode of a conventional zinc-alkaline battery which
employs zinc as the anode active material, aqueous alkaline
solution as the electrolyte, and manganese dioxide, silver oxide,
oxygen and so forth as the cathode active material. The use of such
zinc alloy permits the reduction of the amount of mercury to be
used for amalgamation of the anode zinc surface which is made for
the purpose of corrosion inhibition, thereby enabling the provision
of a low-pollution zinc-alkaline battery.
Inventors: |
Miura; Akira (Katano,
JP), Takata; Kanji (Neyagawa, JP), Okazaki;
Ryoji (Katano, JP), Uemura; Toyohide (Takehara,
JP), Kagawa; Keiichi (Takehara, JP) |
Assignee: |
Matsushita Electric Indus. Co.
Ltd. (Osaka, JP)
Mitsui Mining & Smelting Co., Ltd. (Tokyo,
JP)
|
Family
ID: |
27563902 |
Appl.
No.: |
07/029,343 |
Filed: |
March 19, 1987 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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804821 |
Dec 5, 1985 |
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Foreign Application Priority Data
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Dec 12, 1984 [JP] |
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59-262135 |
Dec 12, 1984 [JP] |
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59-262138 |
Feb 5, 1985 [JP] |
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60-20372 |
Feb 5, 1985 [JP] |
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60-20373 |
Oct 16, 1985 [JP] |
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60-230159 |
Oct 16, 1985 [JP] |
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60-230161 |
Oct 17, 1985 [JP] |
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60-231599 |
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Current U.S.
Class: |
429/206; 429/229;
429/230 |
Current CPC
Class: |
C22C
18/00 (20130101); H01M 4/42 (20130101); Y02E
60/10 (20130101) |
Current International
Class: |
H01M
4/42 (20060101); C22C 18/00 (20060101); H01M
004/40 () |
Field of
Search: |
;429/230,229,206 |
References Cited
[Referenced By]
U.S. Patent Documents
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4376810 |
March 1983 |
Takeda et al. |
4500614 |
February 1985 |
Nagamine et al. |
4585716 |
April 1986 |
Chalilpoyil et al. |
4735876 |
April 1988 |
Miura et al. |
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Foreign Patent Documents
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0003204 |
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1958 |
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JP |
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0022956 |
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1893 |
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GB |
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Primary Examiner: Walton; Donald L.
Attorney, Agent or Firm: Stevens, Davis, Miller &
Mosher
Parent Case Text
This application is a continuation of application Ser. No. 804,821
filed Dec. 5, 1985, now abandoned
Claims
What is claimed is:
1. A zinc-alkaline battery provided with a cathode, an electrolyte
consisting of an aqueous alkali solution, and an anode, in which
the active material of said anode is a zinc alloy powder containing
zinc as the principal component, 0.01 to 0.5% by weight of Ni, 0.01
to 0.5% by weight of In and/or Pb, and 0.01 to 0.2% by weight of
Al.
2. A zinc-alkaline battery according to claim 1, containing 0.1% by
weight of Ni, 0.05% by weight of In, 0.05% by weight of Pb, and
0.05% by weight of Al.
3. A zinc-alkaline battery according to claim 1, wherein the
mercury concentration of the zinc alloy powder is 1.0 to 0.2% by
weight.
Description
TECHNICAL FIELD OF THE INVENTION
This invention relates to an improvement for an zinc-alkaline
battery using zinc as an anode active material, aqueous alkaline
solution as an electrolyte, and manganese dioxide, silver oxide,
mercury oxide, oxygen, or the like as a cathode active material.
More particularly, it relates to a zinc-alkaline battery whch has
enabled reduction of the amount of mercury to be used for
amalgamation of the anode zinc surface by using for the anode a
zinc alloy containing indium (In), lead (Pb), cadmium (Cd), gallium
(Ga), nickel (Ni), aluminum (Al) and alkaline earth metals in a
specified combination.
BACKGROUND OF THE INVENTION
As a problem common to zinc-alkaline batteries, there is raised the
corrosion of the anode zinc caused by the electrolyte. Namely, zinc
is so reactive in an alakli electrolyte as reacting with the
electrolyte during long term storage, thereby undergoing
self-corrosion in accordance with the following equation:
Hydrogen gas generated from the corrosion causes gas pressure in
the battery to elevate, which involves the danger of causing
leakage of electrolyte, bursting and the like. Accordingly, it has
been hitherto adopted as an industrial technique to use amalgamated
zinc powder which was prepared by adding about 5 to 10% by weight
of mercury to zinc, to increase thus the hydrogen overvoltage and
to suppress the corrosion to a practically allowable level. In
recent years, however, it has been a increasing social demand to
decrease the amount of mercury contained in a battery for lowering
environmental pollution, and various studies have been conducted.
For example, methods have been proposed which use zinc alloy powder
formed by adding Pb, Ga, In etc. having high hdyrogen overvoltage
into zinc to improve corrosion resistance and to decrease mercury
concentration rate. These methods are effective to some extent in
corrosion inhibition and give a zinc anode of nearly satisfactory
corrosion resistance until a mercury concentration rate of about 3%
by weight. However, when the mercury concentration rate is further
decreased, zinc anodes obtained by these methods do not have
sufficient corrosion resistance, and hydrogen gas generated during
storage is accumulated on the surface or in the neighborhood of the
anode active material, which causes the deterioration of discharge
performance and can sometimes cause the expansion of the battery or
the leakage of electrolyte, and thus they have a defect of
insufficient storage property.
Further, it has been proposed, mainly with the view of improving
manganese dry batteries, that a good corrosion inhibitory effect
can be obtained by using for an anode a zinc alloy formed by adding
In to zinc or zinc alloy [Japanese Patent application Kokoku
(PostExam. Publn.) No. 3204/58]. The description of the above
proposal includes cases wherein, besides In, one or more elements
selected from Pb, Cd, Al, Mg, iron, chromium, calcium, mercury,
bismuth, antimony, silver, silicon, nickel manganese etc. are added
to zinc as an impurity or as an additive. However, it does not
state clearly whether the above-mentioned various elements are each
contained as in impurity or added as an effective additive except
for the effectiveness of In and Pb used in combination as additive
elements. Further, it neither states which element is effective for
corrosion inhibition, nor shows the suitable amount to be added
except those for In and Pb. Thus, no investigation has ever been
made on the effect of combined use of these elements, particularly
for zinc-alkaline battery, to find an effective zinc alloy
composition.
BRIEF DESCRIPTION OF THE DRAWING
The attached drawing is a side view showing the cross section of a
button-type silver oxide battery using the zinc alloy powder
according to this invention as the anode active material.
List of numerical symbols referred to in the Drawing.
1 : Seal plate,
1': Copper plating layer of the inside surface of seal plate,
2: Zinc anode,
3: Electrolyte absorbent,
4: Separator,
5: Cathode,
6: Cathode ring,
7: Cathode can,
8: Gasket.
SUMMARY OF THE INVENTION
The principal object of this invention is to obtain a zinc-alkaline
battery of low pollution and of excellent overall performance
including discharge performance, storage property and prevention of
alkaline leakage by using for the anode a zinc alloy containing In,
Pb, Cd, Ga, Ni, Al and alkalne earth metals in a specified
combination, thereby decreasing the amalgamation rate without
causing the deterioration of the discharge performance and the
corrosion resistance of the anode.
DETAILED DESCRIPTION OF THE INVENTION
More particularly, this invention is characterized by using a zinc
alloy containing 0.01 to 0.5% by weight in total of at least one of
In, Pb, Cd and Ga, 0.01 to 0.5% by weight of Ni, and optionally,
further, 0.005 to 0.2% by weight of one of Al, magnesium (Mg),
calcium (Ca), barium (Ba) and strontium (Sr) for the anode of the
so-called zinc-alkaline battery, which uses zinc as the anode
active material, an aqueous alkaline solution containing mainly
potassium hydroxide, sodium hydroxide or the like as the
electrolyte, and manganese dioxide, silver oxide, mercury oxide,
oxygen or the like as the cathode active material. In this way,
this invention has attained the realization of a zinc-alkaline
battery of low pollution.
The effect of this invention, which has enabled the attainment of
the above-mentioned object, may be understood, though as a
presumption, as follows.
When molten zinc alloy is pulverized by injection method, its
cooling velocity is very high, namely in the order of 10.sup.2 to
10.sup.3 .degree. C./sec. Consequently, it can be considered that
in a zinc alloy powder containing a proper amount of Ni as
described later in the working examples, Ni will form a homogeneous
mass with zinc although the solubility of Ni in zinc is small.
Accordindgly, it can be presumed that when the zinc alloy is
amalgamated from its surface, Ni, whose affinity for mercury is
low, will suppress the diffusion of mercury into crystals and thus
contribute to maintain the mercury concentration at the zinc alloy
surface at a high level. On the other hand, however, Ni may
possibly affect rather badly the compatibility of mercury with the
zinc alloy surface. However, addition of at least one of In, Pb,
Cd, and Ga, which have the effect of elevating the hydrogen
over-voltage of zinc alloy, to zinc alloy with Ni, enables to form
an amalgamated zinc alloy powder whose surface has been uniformly
amalgamated and at the same to suppress the diffusion of mercury to
the inner part of zinc alloy during storage. Thus, a zinc anode has
been obtained which is of a low mercury concentration rate, namely
3% by weight or less, preferably 2.5 to 0.5% by weight, and
generates little hydrogen gas even in long term storage. Further,
all of Al, Mg, Ca, Ba and Sr suppress the diffusion of mercury to
the inner part of zinc alloy because of their low affinity for
mercury like Ni, and moreover, as their inherent function, have an
effect of smoothening the surface of zinc alloy powder by
preventing the formation of wrinkles which will usually develop
when molten zinc alloy is made into powder by injection, thereby
reducing the surface area. Accordingly, addition of any one of
these elements to above-mentioned zinc alloy containing Ni and at
least one of In, Pb, Cd and Ga improves the corrosion resistance
further. Thus, a zinc anode of further lower mercury concentration
rate, namely, preferably 1.5 to 0.2% by weight, has been obtained.
However, since Al, Mg, Ca, Ba and Sr are all a baser metal than
zinc, they tend to be corroded in preference to zinc in
electrolyte. Accordingly, their amount to be added should be
determined taking into consideration the balance between their
favorable effect expected for corrosion resistance and their
adverse effect. Addition of excessive amount of these elements has
rather an adverse effect on corrosion resistance.
Thus, this invention has enabled to provide a zinc anode which is
of a low mercury concentration rate, i.e. a mercury content of 3%
by weight or less, and is excellent in storage property based on
the experimental investigation of the combination of additional
elements and their amounts to be added to zinc alloy used for an
anode.
PREFERRED EMBODIMENT OF THE INVENTION
Hereunder will be described a process for producing a zinc alloy
powder of this invention and an actual method of using the powder
in a battery as the anode active material.
The zinc alloy powder of this invention can be obtained by a method
which comprises injecting a molten metal with a compressed gas.
More particularly, a zinc base metal of 99.997% purity is molten at
about 500.degree. C., and the respective given amounts of small
pieces of elements to be added are added thereto and dissolved with
stirring to produce a uniform molten alloy. The molten alloy is
injected with compressed gas, such as compressed air, nitrogen gas
or argon gas, of 4 kg/cm.sup.2 pressure in order to pulverize the
alloy. After being sieved to a particle size range of 20 to 150
mesh, the alloy powders are thrown into a 10% by weight aqueous
potassium hydroxide solution, and then amalgamated by dropwise
addition of a given amount of metallic mercury with stirring, and
washed with water. After replacing the water with acetone followed
by vacuum drying, an amalgamated zinc alloy powder is obtained. The
amalgamated zinc alloy powder thus prepared is then added with
stirring to a gel-like elecrolyte, which has been obtained by
gelating an alkali electrolyte with a water-soluble high molecular
substance such as carboxymethyl cellulose, sodium polyacrylate and
the like, to give a uniformly dispersed gel-like anode, and a
predetermined amount thereof is then filled into the anode part by
means of a pump or the like to compose a battery.
EXAMPLE 1
The above-mentioned procedures for preparing the zinc alloy powder
were followed to prepare various kinds of zinc alloy powder (these
being referred to Examples (1) to (32)), in which the combinations
of the added elements were Ni-In, Ni-Pb, Ni-Cd, Ni-Ga, Ni-In--Pb,
Ni-In-Ga, Ni-In-Cd, Ni-Pb-Ga, Ni-Pb-Cd, Ni-Ga-Cd, and
Ni-In-Pb-Cd-Ga, and the proportions of the added elements to zinc
are in the range of 0.01 to 0.5% by weight for Ni, and 0.01 to 0.5%
by weight in total for at least one of In, Pb, Cd and Ga. Further,
there were prepared zinc alloy powders in which the added element
was any one of Ni, In, Pb, Ga and Cd; zinc alloy powders in which
alloy compositions were the same as mentioned above but the
proportions of the added elements were outside the range of the
working examples; and a powder containing no added element. These
were referred to as
COMPARATIVE EXAMPLES (33) to (48).
These zinc alloy powders or zinc powders were amalgamated to a
mercury concentration rate of 1.5% by weight and used to compose a
button-type silver oxide battery shown in the Drawing. In the
Drawing, 1 is a real plate made of stainless steel, whose inner
face has been coated with copper plating 1'; 2 is a zinc anode
manufactured by dispersing the amalgamated zinc powder according to
this invention into a gel which has been prepared by gelating with
carboxymethyl cellulose an electrolyte prepared by saturating
aqueous 40% by weight solution of potassium hydroxide with zinc
oxide; 3 is a cellulosic electrolyte absorbent; 4 is a separator
made of porous polypropylene; 5 is a cathode made by pressmolding a
mixture of silver oxide and graphite; 6 is a cathode ring made of
iron plated with nickel; 7 is a cathode can made of iron, whose
surface is plated with nickel; 8 is a gasket made of nylon and is
compressed between the cathode can and the seal plate by bending
the cathode can. The battery made on experimental basis had a
diameter of 11.6 mm and a height of 5.4 mm. The weights of the
amalgamated zinc alloy powders of the anodes were all fixed at one
value of 193 mg each. In the following Table are shown the
compositions of the zinc alloy of the manufactured battery, the
average values of the discharge performance and the change in the
total height of the battery after 1 month of storage at a
temperature of 60.degree. C. The discharge performance was
expressed in terms of the duration of discharge when the discharge
was conducted at 20.degree. C. and at 510 .OMEGA. down to an end
voltage of 0.9 V. Further, the batteries were allowed to stand at a
temperature of 60.degree. C. and a relative humidity of 90% for one
month and then the state of electrolyte leakage was judged by
visual observation. The number of batteries in which leakage was
observed are also shown in the Table.
__________________________________________________________________________
Change in Number of Added elements and total batteries their
content in Duration of height of showing Battery zinc alloy
discharge battery leakage No. (% by weight) (hrs) (n = 3) (.mu.m)
(n = 20) (n = 20)
__________________________________________________________________________
1 Ni In (0.01) (0.01) 44 -5 0 2 Ni In (0.01) (0.01) 44 -5 0 3 Ni In
(0.01) (0.1) 44 -6 0 4 Ni In (0.01) (0.5) 43 -5 0 5 Ni In (0.05)
(0.01) 44 -6 0 6 Ni In (0.05) (0.1) 44 -6 0 7 Ni In (0.05) (0.5) 43
-5 0 8 Ni In (0.1) (0.01) 44 -5 0 9 Ni In (0.1) (0.1) 45 -7 0 10 Ni
In (0.1) (0.5) 43 -6 0 11 Ni In (0.5) (0.01) 44 -5 0 12 Ni In (0.5)
(0.1) 44 -5 0 13 Ni In (0.5) (0.5) 43 -5 0 14 Ni Pb (0.01) (0.01)
44 -6 0 15 Ni Pb (0.1) (0.1) 43 -5 0 16 Ni Pb (0.5) (0.5) 43 -5 0
17 Ni Cd (0.01) (0.01) 43 -5 0 18 Ni Cd (0.1) (0.1) 44 -6 0 19 Ni
Cd (0.1) (0.1) 43 -6 0 20 Ni Ga (0.01) (0.01) 44 -6 0 21 Ni Ga
(0.1) (0.1) 43 -5 0 22 Ni Ga (0.5) (0.5) 42 -5 0 23 Ni In Pb (0.01)
(0.005) (0.005) 45 -7 0 24 Ni In Pb (0.05) (0.025) (0.025) 45 -8 0
25 Ni In Pb (0.1) (0.05) (0.05) 46 -7 0 26 Ni In Pb (0.5) (0.25)
(0.25) 44 -8 0 27 Ni In Ga (0.1) (0.1) (0.1) 44 -7 0 28 Ni In Cd
(0.1) (0.1) (0.1) 44 -7 0 29 Ni Pb Ga (0.1) (0.1) (0.1) 43 -6 0 30
Ni Pb Cd (0.1) (0.1) (0.1) 44 -7 0 31 Ni Ga Cd (0.1) (0.1) (0.1) 43
-6 0 32 Ni In Pb Cd Ga (0.1) (0.05) (0.05) (0.05) (0.05) 44 -6 0 33
Ni (0.01) 13 +138 20 34 Ni (0.1) 17 +103 20 35 In (0.01) 36 +2 0 36
In (0.1) 37 +1 0 37 Pb (0.1) 32 +4 4 38 Ga (0.1) 30 +6 5 39 Cd
(0.1) 33 +3 3 40 Ni In (0.01) (0.001) 31 +4 4 41 Ni In (0.01) (1.0)
30 +6 4 42 Ni In (0.1) (0.001) 34 +3 2 43 Ni In (0.5) (0.001) 34 +3
3 44 Ni In (0.001) (0.1) 30 +4 4 45 Ni In (1.0) (0.1) 27 +9 6 46 Ni
In Pb (0.001) (0.001) (0.001) 35 +1 0 47 Ni In Pb (1.0) (1.0) (1.0)
31 +1 0 48 None -- -- --
__________________________________________________________________________
With regard to the change in total height of the battery shown in
above Table, it is usual that, after the battery has been sealed,
the total height of the battery continues to decrease until he
balance of stress among the individual components of the battery
becomes stable with lapse of time. However, in batteries wherein a
large amount of hydrogen gas is generated accompanying the
corrosion of zinc anode, there is a stronger tendency for the total
height of battery to be increased by the elevation of intermal
pressure of the battery which couteracts the abovementioned force
of battery. Accordingly, the corrosion resistance of a zinc anode
can be evaluated in terms of increase or decrease of the total
height of the battery during storage. Further, when a battery uses
a zinc anode of insufficient corrosion resistance, in addition to
the increase of the total height of the battery, its resistance to
electrolyte leakage is deteriorated owing to the rise of interval
pressure of the battery and moreover its discharge performance is
markedly deteriorated owing to the consumption of zinc due to
corrosion, the formation of oxidized film on the zinc surface, and
the inhibition of discharge reaction due to the presence of
hydrogen gas in the battery. Thus, duration of discharge also
depends largely on the corrosion resistance of the zinc anode.
Among Comparative Examples shown in the above Table, for the case
(48) wherein no additional element is present, there is indicated
no result for the duration of discharge, the change in total height
of the battery, or the number of batteries showing leakage. This is
because, when no additional element was used, the amount of
hydrogen gas generated during storage was so large that there
occurred extreme expansion in all of the batteries and, further,
bursting or severe leakage of electrolyte occurred in some of the
batteries. Thus, the use of a zinc anode whose mercury content has
been simply decreased to a mercury concentration rate of 1.5% by
weight results in an utterly unusable battery. Further, in
Comparative Examples (33) to (39), wherein only one of the
additional elements shown in the above Example is added, the
batteries have each their problem. Particularly when Ni alone is
added, a large amount of hydrogen gas is generated, and
consequently the batteries expand extremely and leakage of
electrolyte occurs in all of the batteries; moreover discharge
performance after storage is also greatly deteriorated owing to
self-exhaustion and the inhibition of discharge reaction by
occluded gas. In cases of single addition of any one of In, Pb, Ga
and Cd, which are additive elements having an effect of elevating
the hydrogen overvoltage of zinc alloy, although the evolution of
hydrogen gas during storage is relatively small and the expansion
of the battery is also small, leakage occurs in some of the
batteries and also the duration of discharge is short. Thus, the
mere addition of a single element of Ni, In, Pb, Ga, or Cd does not
give, at a low mercury concentration rate of 1.5% by weight, an
anode which is excellent both in corrosion resistance and in
discharge performance even after storage. On the other hand, zinc
alloys (1) to (32) shown in the working examples, which contain Ni
in the range of 0.01 to 0.5% by weight and at the same time at
least one element of In, Pb, Ga and Cd in the range of 0.01 to 0.5%
by weight in total, exhibit remarkable combined effects, are
excellent both in corrosion resistance and discharge performance,
causes no leakage of electrolyte, and thus show practically
satisfactory characteristics. Further, it can be seen from the
comparison of test results obtained between (1) to (13), (14) to
(16), (17) to (19), and (20) to (22), that the combined use of In,
Pb, Cd, or Ga with Ni gives an approximately similar effect and
further, from the results of (23) to (32), that simultaneous
addition of these elements also gives a similar or better
effect.
Comparative Examples (40) to (47) show cases wherein, though the
alloy compositions are the same as those in the working examples,
the contents of added elements are insufficient or excessive. The
results reveal that all of these have problems in corrosion
resistance, discharge performance and prevention of alkaline
leakage.
EXAMPLE 2
The same method of preparation of zinc alloy powders as in Example
1 was used to obtain zinc alloy powders in which the combinations
of the added elements were Ni-In-Al, Ni-Pb-Al, Ni-Ga-Al, Ni-Cd-Al,
Ni-In-Pb--Al, Ni-In-Mg, Ni-In-Ca, Ni-In-Ba, Ni-In-Sr, Ni-Pb-Ca and
Ni-Cd-Sr, and the proportions of the added elements relative to
zinc were in the range of 0.01 to 0.5% by weight for Ni, 0.01 to
0.5% by weight in total for at least one of In, Pb, Cd or Ga, and
0.005 to 0.2% by weight for one of Al, Mg, Ca, Ba or Sr. These were
referred to as Examples (49) to (65). Further, zinc alloy powders
in which added elements and their proportions were respectively the
same as in (9), (15), (25) and (30) of Example 1 were prepared and
referred to as (72), (73), (74) and (75), respectively. Further,
zinc alloy powders were prepared in which added elements were the
same as in above Example 1 but the proportions of added elements
were outside the range of the working examples. These were referred
to as Comparative Examples (66) to (71).
These zinc alloy powders were amalgamated to a mercury
concentration rate of 1.0% by weight and then, in the same manner
as in Example 1, composed into a battery and evaluated.
__________________________________________________________________________
Change in Number of Added elements and total batteries their
content in Duration of height of showing Battery zinc alloy
discharge battery leakage No. (% by weight) (hrs) (n = 3) (.mu.m)
(n= 20) (n = 20)
__________________________________________________________________________
49 Ni In Al (0.01) (0.01) (0.005) 43 -6 0 50 Ni In Al (0.1) (0.1)
(0.05) 45 -7 0 51 Ni In Al (0.5) (0.5) (0.2) 44 -5 0 52 Ni Pb Al
(0.01) (0.01) (0.005) 43 -5 0 53 Ni Pb Al (0.1) (0.1) (0.05) 45 -7
0 54 Ni Pb Al (0.5) (0.5) (0.2) 44 -6 0 55 Ni Ga Al (0.1) (0.1)
(0.05) 44 -6 0 56 Ni Cd Al (0.1) (0.1) (0.05) 44 -7 0 57 Ni In Pb
Al (0.01) (0.005) (0.005) (0.005) 43 -6 0 58 Ni In Pb Al (0.1)
(0.05) (0.05) (0.05) 45 -7 0 59 Ni In Pb Al (0.5) (0.25) (0.25)
(0.2) 44 -6 0 60 Ni In Mg (0.1) (0.1) (0.05) 43 -5 0 61 Ni In Ca
(0.1) (0.1) (0.05) 44 -6 0 62 Ni In Ba (0.1) (0.1) (0.05) 44 -6 0
63 Ni In Sr (0.1) (0.1) (0.05) 44 -7 0 64 Ni Pb Ca (0.1) (0.1)
(0.05) 43 -5 0 65 Ni Cd Sr (0.1) (0.1) (0.05) 44 -7 0 66 Ni In Al
(0.001) (0.001) (0.001) 31 +4 3 67 Ni In Al (1.0) (1.0) (0.5) 30 +7
6 68 Ni Pb Al (0.001) (0.001) (0.05) 27 +13 11 69 Ni Pb Al (1.0)
(1.0) (0.5) 29 +10 9 70 Ni In Pb Al (0.001) (0.001) (0.001) (0.001)
33 +3 1 71 Ni In Pb Al (1.0) (0.5) (0.5) (0.5) 30 +8 6 72 Ni In
(0.1) (0.1) 41 -4 0 73 Ni Pb (0.1) (0.1) 40 -3 0 74 Ni In Pb (0.1)
(0.05) (0.05) 40 -4 0 75 Ni Pb Cd (0.1) (0.1) (0.1) 41 -3 0
__________________________________________________________________________
As can be seen from the above Table, even at a low mercury
concentration rate of 1.0% by weight, zinc alloys (49) to (65),
which contain Ni in the range of 0.01 to 0.5% by weight, at least
one element of In, Pb, Ga and Cd in the range of 0.01 o 0.5% be
weight in total, and further one element of Al, Mg, Ca, Ba and Sr
in the range of 0.005 to 0.2% by weight, exhibit marked combined
effect, and are excellent in corrosion resistance, discharge
performance, and resistance to electrolyte leakage. Further, alloy
powders having compositions of Example 1 which contain none of Al,
Mg, Ca, Ba and Sr also exhibit characteristics satisfactory in
practice, though they are somewhat inferior in discharge
performance to alloys (49) to (65) of Example 2. On the other hand,
in Comparative Example (66) to (71), wherein though the alloy
compositions are the same as in Example 2, the contents of added
elements are insufficient or excessive, all of the alloys have
problems in corrosion resistance, discharge property, and
resistance to electrolyte leakage.
As described above, this invention has developed a zinc-alkaline
battery of low pollution and off excellent practical performance by
finding the contents of elements to be added which will give
effectively a synergistic effect in zinc alloy powders containing
Ni and at least one of In, Pb, Ga and Cd, and further, optionally,
one of Al, Mg, Ca, Ba and Sr.
Although this invention was illustrated with reference to a silver
oxide battery in Examples, the zinc alloy powder according to this
invention can also be applied to other zinc-alkaline batteries
using zinc as the anode. Particularly in the case of open-type air
batteries or closed-type alkali-manganese batteries provided with a
hydrogen-absorption system, in which the allowable amount of
evolving hydrogen gas is relatively large, the zinc alloy can be
used at a low mercury concentration rate of less than 1.0% by
weight, or as low as 0.2% by weight and, under certain
circumstances, even without amalgamation.
As described above, according to this invention, the mercury
concentration rate of anode zinc can be decreased and a
low-pollution zinc-alkaline battery can be manufactured very
easily.
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